U.S. patent number 7,121,722 [Application Number 10/835,473] was granted by the patent office on 2006-10-17 for temperature sensor.
This patent grant is currently assigned to NGK Spark Plug Co., Ltd.. Invention is credited to Go Hanzawa, Masahiko Nishi.
United States Patent |
7,121,722 |
Hanzawa , et al. |
October 17, 2006 |
Temperature sensor
Abstract
A temperature sensor comprising: a flange having a bore and
mounted on a fluid pipe having a fluid flow, to prevent said fluid
from leaking out; an MI cable formed to have metallic cores
insulated and retained on a metallic outer cylinder, and fixed in
such a mode in said bore that a leading end side of said MI cable
protrudes from a leading end side of said flange and extends in an
axial direction; a metallic cap fixed on a leading end side outer
circumference of said MI cable and having fluid communication ports
for allowing said fluid to flow therein; and a temperature sensing
element including: a ceramic substrate housed in said cap; a
sensing portion formed over said ceramic substrate and having
electric characteristics varied with a temperature of said fluid;
and a wiring portion for connecting said sensing portion and said
metallic cores of said MI cable electrically.
Inventors: |
Hanzawa; Go (Aichi,
JP), Nishi; Masahiko (Aichi, JP) |
Assignee: |
NGK Spark Plug Co., Ltd.
(Aichi, JP)
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Family
ID: |
33308220 |
Appl.
No.: |
10/835,473 |
Filed: |
April 30, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040218662 A1 |
Nov 4, 2004 |
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Foreign Application Priority Data
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May 2, 2003 [JP] |
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P.2003-127448 |
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Current U.S.
Class: |
374/185; 374/208;
374/148; 374/E13.006 |
Current CPC
Class: |
G01K
13/02 (20130101); G01K 2205/04 (20130101) |
Current International
Class: |
G01K
13/00 (20060101); G01K 7/16 (20060101) |
Field of
Search: |
;374/185,148,138,144,178-179,183,208 ;338/22SD |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2178606 |
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Feb 1987 |
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GB |
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04276530 |
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Oct 1992 |
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JP |
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2001056256 |
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Feb 2001 |
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JP |
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2002-168701 |
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Jun 2002 |
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JP |
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Primary Examiner: Guadalupe-McCall; Yaritza
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
What is claimed is:
1. A temperature sensor comprising: a flange having a bore and
mounted on a fluid pipe having a fluid flow, to prevent said fluid
from leaking out; a cable formed to have metallic cores retained
inside a metallic outer cylinder and insulated from each other and
the metallic outer cylinder, and fixed in such a mode in said bore
that a leading end side of said cable protrudes from a leading end
side of said flange and extends in an axial direction; a metallic
cap fixed on a leading end side outer circumference of said cable
and having fluid communication ports for allowing said fluid to
flow therein; and a temperature sensing element including: a
ceramic substrate housed in said cap; a sensing portion formed over
said ceramic substrate and having electric characteristics varied
with a temperature of said fluid; and a wiring portion for
connecting said sensing portion and said metallic cores of said
cable electrically; wherein said ceramic substrate is so housed in
said cap that a rear end of said ceramic substrate is on a more
rear side than a trailing end of said fluid communication ports
formed in a side wall of said cap, and wherein a shielding portion
for preventing said fluid from invading a region on a more rear
side than a trailing end of said ceramic substrate is disposed in
said cap between a trailing end of said fluid communication ports
formed in said side wall of said cap and a leading end face of said
outer cylinder of said cable.
2. The temperature sensor according to claim 1, wherein said
ceramic substrate has a smaller width perpendicular to an axial
direction thereof, as seen along a planar direction of a face to
have said sensing portion, than an external diameter of said outer
cylinder of said cable.
3. The temperature sensor according to claim 2, wherein the
shielding portion is disposed so as to cover said rear end of said
ceramic substrate.
4. The temperature sensor according to claim 2, wherein said
shielding portion is made mainly of glass.
5. The temperature sensor according to claim 1, wherein said
ceramic substrate has a ratio W/L3 of a width W perpendicular to an
axial direction thereof, as seen along a planar direction of a face
to have said sensing portion, to an axial length L3 thereof; and
wherein said ratio W/L3 is in a range of 0.2 to 4, and both said
length L3 and said width W are at most 10 mm.
6. The temperature sensor according to claim 2, wherein said
ceramic substrate has a ratio W/L3 of a width W perpendicular to an
axial direction thereof as seen along a planar direction of a face
to have said sensing portion, to an axial length L3 thereof; and
wherein said ratio W/L3 is in a range of 0.2 to 4, and both said
length L3 and said width W are at most 10 mm.
7. The temperature sensor according to claim 1, wherein the
shielding portion is disposed so as to cover said rear end of said
ceramic substrate.
8. The temperature sensor according to claim 1, wherein said
shielding portion is made mainly of glass.
9. The temperature sensor according to claim 1, wherein a
vibration-proofing portion for retaining at least said metallic
cores of said cable is disposed in a space between a leading end
face of said outer cylinder of said cable and a trailing end face
of said ceramic substrate.
10. The temperature sensor according to claim 1, wherein said
sensing portion of said temperature sensing element is made of a
metallic resistor composed mainly of platinum.
11. The temperature sensor according to claim 1, wherein said cable
is a mineral insulated cable.
12. The temperature sensor according to claim 1, wherein the
ceramic substrate is entirely housed in the cap.
13. A temperature sensor comprising: a flange having a bore and
mounted on a fluid pipe having a fluid flow, to prevent said fluid
from leaking out; a cable formed to have metallic cores retained
inside a metallic outer cylinder and insulated from each other and
the metallic outer cylinder, and fixed in such a mode in said bore
that a leading end side of said cable protrudes from a leading end
side of said flange and extends in an axial direction; a metallic
cap fixed on a leading end side outer circumference of said cable
and having fluid communication ports for allowing said fluid to
flow therein; and a temperature sensing element including: a
ceramic substrate housed in said cap; a sensing portion formed over
said ceramic substrate and having electric characteristics varied
with a temperature of said fluid; and a wiring portion for
connecting said sensing portion and said metallic cores of said
cable electrically; wherein said ceramic substrate has a ratio W/L3
of a width W perpendicular to an axial direction thereof, as seen
along a planar direction of a face to have said sensing portion, to
an axial length L3 thereof said ratio is in a range of 0.2 to 4,
and both said length L3 and said width W are at most 10 mm.
14. The temperature sensor according to claim 1, wherein the
shielding portion is arranged in the cap.
15. The temperature sensor according to claim 13, wherein the
ceramic substrate is entirely housed in the cap.
Description
FIELD OF THE INVENTION
The present invention relates to a temperature sensor. The
temperature sensor of the invention is used suitably for the case,
in which a temperature sensing element is arranged in a fluid pipe
to have a fluid (e.g., an exhaust gas) flow such as the inside of a
catalytic converter or an exhaust pipe of an exhaust gas cleaning
system of an automobile, thereby to detect the temperature of the
fluid.
BACKGROUND OF THE INVENTION
In the prior art, there has been known a temperature sensor, as
called the "exhaust temperature sensor", which is disposed in the
exhaust pipe of the vehicle and used for detecting the temperature
of the exhaust gas. Moreover, a known temperature sensor of this
kind has a structure, in which a ceramic substrate having a
metallic resist or made of a material of a platinum-group is
mounted as a temperature sensing portion (as referred to
JP-A-2002-168701).
A detailed construction of the temperature sensor is shown in FIG.
7. A ceramic substrate 81 is fixed by a holding member 90 in a
cylindrical case 80 made of a metal. The ceramic substrate 81 is
formed into a slender plate shape having wiring layers 81a applied
on its one face, as shown in FIG. 8. A metallic resistor 82 made of
a thermistor material of a platinum group or the like is printed on
the leading end side of the ceramic substrate 81. On the trailing
end side of the ceramic substrate 81, there are fixed terminals 83,
which are electrically connected with the metallic resistor 82
through the wiring layers 81a. The terminals 83 of the ceramic
substrate 81 are connected with the cores 92 of an Mineral
Insulated ("MI") cable 91 extending through a spacer 93 from the
case 80, as shown in FIG. 7. At a position of a length L1 from the
leading end of the case 80, on the other hand, there is formed a
flange portion 80a, around which a nut 94 is turnably mounted. On
the leading end side of this flange portion 80a, there is formed a
seal surface 80c, which makes close contact with the mounting seat
face of the exhaust pipe thereby to prevent the exhaust gas from
leaking out. In the leading end side of the case 80, moreover,
there are formed a plurality of fluid communication ports 80b for
providing the communication of the exhaust gas with the inside of
the case 80. Here, the MI cable 91 is called the "sheath core",
too, and is provided with the cores 92 inside of a cylindrical
outer cylinder made of a metal. This outer cylinder is insulated
and filled with ceramics or the like so that the cores 92 are held
while being insulated from the outer cylinder.
In this temperature sensor, the metallic resistor 82 outputs a
resistance varying with the temperature of the exhaust gas, as an
electric signal, which is extracted to the outside of the case 80
by the cores 92 of the MI cable 91. Thus, the temperature of the
exhaust gas is measured by the temperature sensor so that the
engine or the like of the vehicle is properly controlled according
to the measured temperature.
SUMMARY OF THE INVENTION
In case the fluid pipe such as the exhaust pipe having the fluid
flow has different diameters or in case the fluid temperature is
detected at different positions in the fluid pipe, however, it is
difficult to change a length (or a leg length) L1 from the leading
end of the temperature sensor to the seal surface 80c for the fluid
pipe. More specifically, in case the axial length L1 of that
portion of the temperature sensor which is exposed to the inside of
the fluid pipe has to be changed according to the demand of a user,
it is necessary either to change the length of the ceramic
substrate 81 while changing the length of the case 80 or to change
the length of the MI cable 91. This may make it necessary to
prepare cases 80 or ceramic substrates 81 of different lengths at
all times. This preparation may not only cause troubles but also
raise the manufacture cost. If the change is made to enlarge the
length of the ceramic substrate 81, moreover, this ceramic
substrate 81 has an axially slender shape and may lower its
vibration-proofing properties.
The present invention has been conceived in view of the background
of the prior art thus far described and has an object to provide a
temperature sensor capable of easily changing the axial length (or
the leg length) of its portion be exposed to a fluid pipe having a
fluid flow, to lower its manufacture cost and to retain the
vibration-proofing properties of a ceramic substrate.
According to the invention, there is provided a temperature sensor
comprising:
a flange having a bore and mounted on a fluid pipe having a fluid
flow, to prevent the fluid from leaking out;
an MI cable formed to have metallic cores insulated and retained on
a metallic outer cylinder, and fixed in such a mode in the bore
that its own leading end side protrudes from the leading end side
of the flange and extends in the axial direction;
a metallic cap fixed on the leading end side outer circumference of
the MI cable and having fluid communication ports for allowing the
fluid to flow therein; and
a temperature sensing element including: a ceramic substrate housed
in the cap; a sensing portion formed over the ceramic substrate and
having electric characteristics varied with the temperature of the
fluid; and a wiring portion for connecting the sensing portion and
the metallic cores of the MI cable electrically.
In the temperature sensor of the invention, the cap is directly
fixed on the leading end side outer circumference of the MI cable,
which is fixed in such a mode in the bore as to protrude from the
leading end side of the flange, and the temperature sensing element
having the sensing portion on the ceramic substrate housed in the
cap is electrically connected with the metallic cores of the MI
cable. In case the axial length (or the leg length) of that portion
of the temperature sensor, which is to be exposed to the inside of
the fluid pipe having the fluid flow, has to be changed, therefore,
it is sufficient to cut the MI cable (i.e., the outer cylinder of
the MI cable) to a necessary length thereby to change the length of
the MI cable protruding from the leading end side of the flange. In
this temperature sensor, moreover, the axial length of the ceramic
substrate need not be changed to cause no trouble in the
vibration-proofing problem, which accompanies the change in the
axial length of the ceramic substrate.
According to the temperature sensor of the invention, therefore,
the change in the axial length (or the leg length) of that portion
of the temperature sensor, which is to be exposed to the inside of
the fluid pipe, can be easily made merely by adjusting the axial
length of the MI cable, thereby to lower the manufacture cost. On
the other hand, this temperature sensor is designed to need no
change in the axial length of the ceramic substrate for the change
in the leg length, so that the vibration-proofing properties of the
ceramic substrate can also be retained when the temperature sensor
is to be used. In this temperature sensor, moreover, the cap for
arranging the temperature sensing element has the fluid
communication port formed for allowing the fluid to flow into the
cap. It is, therefore, possible to realize a highly precise
temperature detection, which is excellent in the responsibility of
the temperature sensing element (or the temperature sensing
portion) to the change in the fluid temperature.
Here, the temperature sensing portion to construct the temperature
sensing element is not especially limited, if its electric
characteristics change depending on the temperature of the fluid
(e.g., the exhaust gas). However, it is preferred from the
viewpoint of the high temperature dependency of the electric
resistance and from the chemical stability and the excellent heat
resistance that the temperature sensing portion is made of a
metallic resistor composed mainly of platinum. This metallic
resistor composed mainly of platinum can be formed over the ceramic
substrate by either a thick film method such as a screen printing
method or a thin film method such as a sputtering or a vapor
deposition. Considering the miniaturization of a pattern or the
manufacturing dispersion of the pattern, it is preferred to form
the metallic resistor in a thin film over the ceramic
substrate.
In the temperature sensor of the invention, moreover, it is
preferred that the ceramic substrate has a smaller width
perpendicular to the axial direction thereof, as seen along the
planar direction of the face to have the sensing portion, than the
external diameter of the outer cylinder of the MI cable. As a
result, the cap to be fixed on the leading end side outer
circumference of the MI cable can be reduced in size (or in
diameter) so that the temperature sensor itself can be small-sized.
In the temperature sensor of the invention, moreover, the cap for
housing the temperature sensing element can be diametrically
reduced to improve the responsibility of the temperature
detection.
In the temperature sensor of the invention, moreover, it is
preferred that the ceramic substrate has a ratio W/L3 of the width
W perpendicular to the axial direction thereof, as seen along the
planar direction of the face to have the sensing portion, to the
axial length L3 thereof is 0.2 to 4, and that both the length L3
and the width W are at most 10 mm. With the ratio W/L3 thus being
0.2 to 4, it is possible to make the vibration-proofing properties
of the ceramic substrate stabler. With the length L3 and the width
W being at most 10 mm, moreover, the heat capacity of the ceramic
substrate can be reduced to improve the responsibility of the
temperature detection. Here, it is preferred that the ceramic
substrate has a smaller thickness of 5 mm or less than the values
L3 and W.
In the temperature sensor of the invention, moreover, the ceramic
substrate may be so housed in the cap that its own rear end is on
the more rear side than the trailing end of a fluid communication
port formed in the side wall of the cap, and a shielding portion
for preventing the fluid from invading a region on the more rear
side than the trailing end of the ceramic substrate may be disposed
in the cap between the trailing end of the fluid communication port
formed in the side wall of the cap and the leading end face of the
outer cylinder of the MI cable.
Here in case the wiring portions of the temperature sensing portion
and the metallic cores of the MI cable are connected in the cap,
the conductive path including the metallic cores of the MI cable is
exposed to the internal region (or space) between the trailing end
face of the ceramic substrate composing the temperature sensing
element and the leading end face of the outer cylinder of the MI
cable. If the fluid communication port is formed in the cap housing
the temperature sensing element is formed to improve the
responsibility of the temperature sensing element, therefore, the
exposed conductive path is directly exposed to the fluid introduced
from the fluid communication port into the cap. On the other hand,
the fluid such as the exhaust gas coming from the internal
combustion engine may contain a foreign substance such as moisture
or soot. As a result, the foreign substance may pass through the
fluid communication port and stick to the exposed conductive path
thereby to invite a trouble such as a short-circuiting in the
conductive path.
According to the temperature sensor of the invention, on the
contrary, the shielding portion is provided for shielding the
invasion of the fluid from the trailing end of the ceramic
substrate into the rear side region. As a result, the fluid is not
exposed to the conductive path including the metallic cores of the
MI cable positioned on the more rear side in the cap than the
ceramic substrate, so that the foreign substance in the fluid can
be prevented from sticking to the conductive path. Even in case the
fluid communication port is formed in the cap, therefore, the
short-circuiting trouble of the conductive path can be prevented to
provide a temperature sensor, which is excellent in the electric
reliability while improving the responsibility. Here, it is
preferred that the shielding portion is made of an insulating
heat-resisting material such as mainly of glass.
In the temperature sensor of the invention, moreover, it is
preferred that a vibration-proofing portion for retaining at least
the metallic cores of the MI cable is disposed in the space between
the leading end face of the outer cylinder of the MI cable and the
trailing end face of the ceramic substrate. By providing that
vibration-proofing portion, the metallic cores of the MI cable can
be stably held in the cap so that the metallic cores of the MI
cable can be reliably prevented from being broken at the using time
of the temperature sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a temperature sensor of Embodiment
1;
FIG. 2 is an enlarged sectional view of a portion of the
temperature sensor of Embodiment 1;
FIG. 3 is a perspective view of a ceramic substrate according to
the temperature sensor of Embodiment 1;
FIG. 4 is a sectional view of a temperature sensor of Embodiment
2;
FIG. 5 is an enlarged sectional view of a portion of the
temperature sensor of Embodiment 2;
FIG. 6 is a perspective view of a ceramic substrate according to
the temperature sensor of Embodiment 2;
FIG. 7 is a sectional view of a temperature sensor of the related
art; and
FIG. 8 is a perspective view of a ceramic substrate according to
the temperature sensor of the related art.
DESCRIPTION OF REFERENCE NUMERALS AND SIGNS
100, 300 - - - TEMPERATURE SENSOR 7 - - - FLANGE 7a - - - BORE 7b -
- - SEAL SURFACE 3 - - - MI CABLE 3a - - - OUTER CYLINDER 4 - - -
METALLIC CORES (CORES) 1, 400 - - - CAP 401 - - - LEADING END SIDE
CAP 402 - - - TRAILING END SIDE CAP 1a, 1b, 401a, 401b - - - FLUID
COMMUNICATION PORT 20, 200 - - - TEMPERATURE SENSING ELEMENT 2, 22
- - - CERAMIC SUBSTRATE 2a, 22a - - - SENSING PORTION (METALLIC
RESISTOR) 2b, 2c, 22b - - - WIRING PORTION (2b - - - ELECTRODE
WIRE, 2c - - - WIRING LAYER) 5 - - - VIBRATION-PREVENTING PORTION 6
- - - SHIELDING PORTION 11 - - - HOUSING 13 - - - LEAD WIRES
DETAILED DESCRIPTION OF THE INVENTION
Embodiments 1 and 2 of the invention will be described with
reference to the accompanying drawings.
[Embodiment 1]
A temperature sensor 100 of Embodiment 1 is constructed, as shown
in FIG. 1, to include a flange 7, an MI cable 3, a cap 1, and a
temperature sensing element 20 having a temperature sensing portion
2a formed over a ceramic substrate 2.
More specifically, the flange 7 of SUS310S is fixed on the leading
end side of a cylindrical housing 11 made of SUS304 and is mounted
on a vehicular exhaust pipe to have an exhaust gas flow by a nut
10, which is to be turned on the outer circumference of the housing
11. This nut 10 has an external thread 10a and a hexagonal nut
portion 10b, so that the flange 7 is mounted on the mounting
portion of the exhaust pipe by fastening the external thread 10a on
the internal thread of the mounting portion of the not-shown
exhaust pipe. As a result, the temperature sensor 100 is fixed as a
whole to the exhaust pipe. Moreover, the flange 7 is composed of: a
sheath portion 7d having a bore 7a and extending in the axial
direction; and a bulging portion 7c positioned on the leading end
side of the sheath portion 7d and bulging radially outward. The
bulging portion 7c is formed into an annular shape having such a
tapered seal surface 7b on its leading end side as mates with a
counter-tapered mounting face of the mounting portion of the
not-shown exhaust pipe. When the nut 10 is mounted on the mounting
portion of the exhaust pipe, the seal surface 7b comes into mating
engagement with the mounting seat surface of the mounting portion
to prevent the exhaust gas from leaking to the outside. On the
other hand, the sheath portion 7d is inserted into the housing 11
and is fixed gas-tight in the housing 11 by a laser
welding-all-around.
The MI cable 3 is fixed in the bore 7a of the flange 7 and extended
from the leading end side and the trailing end side of the flange
7. Here, the MI cable 3 is formed in such a mode that a pair of
cores (or metallic cores) 4 made of SUS310S are insulated and
retained through insulating powder (i.e., SiO.sub.2 powder in this
embodiment) in an outer cylinder 3a made of SUS310S. The bottomed
cylindrical cap 1 made of SUS310S is fixed on the outer
circumference of the leading end side of that MI cable 3 by a laser
welding-all-around. The axial length from the leading end of the
cap 1 to the leading end edge of the seal surface 7b of the flange
7 (that is, the axial length of such a portion of the temperature
sensor 100 as to be exposed to the inside of the exhaust pipe) is
set at L2 (mm).
Here, the MI cable 3 is fixed in the bore 7a of the flange 7 by
laser welding-all-around it to the sheath portion 7d of the flange
7. In the cap 1, a plurality of fluid communication ports 1a are
formed in a bottom wall 31 introducing a fluid to be measured into
the cap 1, and a plurality of fluid communication ports 1b having a
similar function are formed in a side wall 32. The temperature
sensing element 20 is housed in the leading end portion of the cap
1.
The ceramic substrate 2 of alumina composing the temperature
sensing element 20 is sized such that a width W perpendicular to
the axial direction, as seen along the planar direction of the face
to have the later-described metallic resistor 2a, is smaller than
the external diameter W1 of the outer cylinder 3a of the MI cable 3
(that is, W=2 mm and W1=2.5 mm in this embodiment). The exterior
view of the temperature sensing element 20 is shown in FIG. 3. In
the ceramic substrate 2 in the temperature sensing element 20, the
ratio W/L3 of the width W perpendicular to the axial direction to
the length L3 in the axial direction is 2/3 (that is, W=2 mm and
L3=3 mm in this embodiment). Here, the ceramic substrate 2 has a
thickness set to a smaller value (e.g., 0.5 mm in this embodiment)
than those of the aforementioned values L3 and W.
On one face of the ceramic substrate 2, moreover, there is formed
the metallic resistor 2a, which is made mainly of Pt having a
resistance varying with the temperature of the exhaust gas. Here,
this metallic resistor 2a is formed into a thin film having a
predetermined pattern shape (e.g., a meandering pattern in this
embodiment, although not shown) and is coated with a protective
film (although not shown) of glass or the like. On that face of the
ceramic substrate 2, there are formed two wiring layers 2c, which
are connected with the metallic resistor 2a. Moreover, a pair of
electric wires 2b are jointed one-by-one to the wiring layers 2c,
and the connected portions (or the overlapping portions) between
the wiring layers 2c and the electric wires 2b are coated with a
protective film 2d made of glass or the like. As a result, the
resistance of the metallic resistor 2a varying with the temperature
is outputted as an electric signal to the electric wires 2b through
the wiring layers 2c. In this embodiment, the electric wires 2b and
the wiring layers 2c correspond to a wiring portion in the Claims,
and the metallic resistor 2a correspond to a sensing portion.
As shown in FIG. 2, the metallic resistor 2a and the paired cores 4
of the MI cable 3 are electrically connected by welding the paired
electric wires 2b of the temperature sensing element 20 to ends 4a
of the cores 4 of the MI cable 3. At this time, the temperature
sensing element 20 is so housed in the cap 1 that the trailing end
(or the trailing end face) 2e of its ceramic substrate 2 is
positioned on the more rear side than the trailing end 1c of that
of the fluid communication ports 1 formed in the side wall 31 of
the cap 1, which is positioned on the most trailing end side.
In the cap 1 and between the leading end face of the outer cylinder
3a of the MI cable 3 and the trailing end face 2e of the ceramic
substrate 2, moreover, there are disposed a vibration-proofing
portion 5 made of insulating cement and a shielding portion 6 made
of crystallized glass (e.g., borosilicate glass) and positioned on
the leading end side of the vibration-proofing portion 5 and on the
more rear side than the trailing end 1c of that of the fluid
communication ports 1b formed in the side wall 31 of the cap 1,
which is positioned on the most trailing end side. Moreover, the
vibration-proofing portion 5 stably holds the cores 4 of the MI
cable 3 arranged in the cap 1 and the connected portions between
the cores 4 of the MI cable 3 and the electric wires 2b of the
temperature sensing element 20. Here in this embodiment, the cement
forming a body portion 6a is composed of an aggregate made mainly
of alumina and a glass component.
By forming the shielding portion 6 in the cap 1, moreover, the
inside region of the cap 1 is defined across the shielding portion
6 into the front side and the rear side. Even in case the fluid
communication ports 1a and 1b are formed in the cap 1, therefore,
the exhaust gas introduced into the cap 1 is blocked by the
shielding portion 6 from invading the region on the more rear side
than the trailing end 2e of the ceramic substrate 2. As a result, a
foreign substance such as a moisture content contained in the
exhaust gas can be effectively prevented from sticking to the
conductive paths, which are composed of the electric wires 2b and
the cores 4 and positioned on the rear side of the ceramic
substrate 2.
Moreover, the vibration-proofing portion 5 of cement and the
shielding portion 6 of crystallized glass can be formed in the cap
1 in the following manner. First of all, the electric wires 2b of
the temperature sensing element 20 and the cores 4a of the MI cable
3 are welded to each other. After this, the cap 1 having the fluid
communication ports 1a and 1b formed in advance are so fixed by a
laser welding-all-around to the outer cylinder 3a of the MI cable 3
as to cover the temperature sensing element 20. After this, a
predetermined amount of unsolidified cement is poured into the
fluid communication ports 1a formed in the bottom wall 31 of the
cap 1, and is dried and solidified to form the vibration-proofing
portion 5. Subsequently, a predetermined amount of glass powder is
poured into the same fluid communication ports 1a and is subjected
to a heat treatment to form the shielding portion 6.
As shown in FIG. 1, the other ends 4b of the MI cable 3 are fixed
on connecting terminals 14 in the housing 11. Moreover, one-side
ends 13a of a pair of lead wires 13 are fixed on the connecting
terminals 14. The other ends 4b of the cores 4 and the one-side
ends 13a of the lead wires 13 are covered with insulating tubes 15
together with the connecting terminals 14. Moreover, a grommet 12
made of heat-resisting rubber is caulked in the trailing end side
of the housing 11. The paired lead wires 13 are extended through
the grommet 12 from the trailing end side of the housing 11.
In the temperature sensor 100 of Embodiment 1 thus constructed, the
cap 1 is directly fixed on the outer circumference of the leading
end side of the MI cable 3, which is so fixed in the bore 7a of the
flange 7 that it is protruded from the leading end side of the
flange 7, and the temperature sensing element 20 having the
metallic resistor 2a on the ceramic substrate 2 housed in that cap
1 is electrically connected with the cores 4 of the MI cable 3. In
case the axial length (or the leg length) L2 of that portion of the
temperature sensor 100, which is to be exposed to the inside of the
fluid pipe (or the exhaust pipe) to have the fluid (or the exhaust
gas) flow, is to be changed, therefore, the MI cable 3 (i.e., the
outer cylinder 3a of the MI cable 3) may be cut to a necessary
length thereby to change the its length protruded from the leading
end side of the flange 7. In this temperature sensor 100, moreover,
the axial length of the ceramic substrate 2 need not be changed to
cause none of the vibration-proofing trouble, which might otherwise
accompany the change in the axial length of the ceramic substrate
2.
In this temperature sensor 100, moreover, the ceramic substrate 2
is sized such that the width W perpendicular to the axial
direction, as seen along the planar direction of the face to have
the metallic resistor 2a, is smaller than the external diameter W1
of the outer cylinder 3a of the MI cable 3. Therefore, the cap 1
fixed on the outer circumference of the leading end side of the MI
cable 3 can be reduced in size (i.e., in diameter) so that the
temperature sensor 100 itself can be small-sized. In this
temperature sensor 100, moreover, the cap 1 housing the temperature
sensing element 20 can be diametrically reduced to improve the
responsibility of the temperature detection.
In this temperature sensor 100, moreover, the ratio W/L3 of the
width W of the ceramic substrate 2 in the temperature sensing
element 20, as taken perpendicularly of the axial direction, to the
length L3 in the axial direction is 2/3 (that is, W=2 mm and L3=3
mm in this embodiment), and the thickness of the ceramic substrate
2 set to a smaller value (e.g., 0.5 mm in this embodiment) than
those of the aforementioned values L3 and W. By thus setting the
aforementioned ratio W/L3 within a range of 0.2 to 4, the
vibration-proofing properties of the ceramic substrate 2 can be
made stabler. By setting the length L3 and the width W at 10 mm or
less and the thickness of the ceramic substrate 2 smaller than the
values L3 and W, moreover, the heat capacity of the ceramic
substrate 2 can be reduced to improve the responsibility of the
temperature detection.
According to the temperature sensor 100 of Embodiment 1, therefore,
the axial length (or the leg length) L2 of that portion of the
temperature sensor 100, which is to be exposed to the inside of the
fluid pipe (or the exhaust pipe), can be easily changed by
adjusting the axial length of the MI cable 3, so that the
manufacture cost can be lowered. Moreover, this temperature sensor
100 is designed to need no change in the axial length of the
ceramic substrate 2 for changing the leg length L2, so that the
vibration-proofing properties of the ceramic substrate 2 can be
retained when the temperature sensor 100 is used.
[Embodiment 2]
As shown in FIG. 4, a temperature sensor 300 of Embodiment 2 has a
construction similar to that of temperature sensor 100 shown in
FIG. 1, excepting that a temperature sensing element 200 is
different from that of the temperature sensor 100 of Embodiment 1.
The description of the temperature sensor 300 will be omitted by
designating the components identical to those of Embodiment 1 shown
in FIG. 1.
The exterior view of the temperature sensing element 200 to be used
in the temperature sensor 300 of Embodiment 2 is shown in FIG. 6.
The ratio W/L3 of the width W perpendicular to the axial direction,
as seen along the planar direction of the face to have a metallic
resistor 22a, to the axial length L3 of a ceramic substrate 22
composing the temperature sensing element 200 is 2 (that is, W=3.2
mm and L3=1.6 mm in this embodiment). Here, the ceramic substrate
22 is made of alumina and has a thickness set to a smaller value
(as specified by 0.5 mm) than those of the aforementioned values L3
and W.
At the center of the ceramic substrate 22, moreover, there is
formed the metallic resistor 22a, which is made mainly of Pt having
a resistance varying with the temperature of the exhaust gas. On
the ceramic substrate 2 and close to the two end portions, there
are formed two film-shaped wiring portions 22b, which are connected
with the metallic resistor 22a. Those two wiring portions 22b are
individually jointed and connected with the paired cores 4 of the
MI cable 3. As a result, the resistance of the metallic resistor
22a varying with the temperature is outputted as an electric signal
to the cores 4 of the MI cable 3 through the wiring portions 22b.
Here, the metallic resistor 22a and the connected portions between
the wiring portions 22b and the cores 4 are coated with the
(not-shown) protective film made of glass or the like. In
Embodiment 2, the outer cylinder 3a of the MI cable 3 has an
external diameter of 3.3 mm.
In the temperature sensor 300 of Embodiment 2, as shown in FIG. 5,
the cylindrical cap 400 is formed of a double structure, which is
constructed of a bottomed cylindrical leading end side cap 401 and
a trailing end side cap 402 having two open ends. More
specifically, the trailing end side cap 402 is fixed on the outer
side of the outer cylinder 3a of the MI cable 3 by the laser
welding-all-around, and the leading end side cap 401 is fixed on
the outer side of the trailing end side cap 402 by the laser
welding-all-around. In the leading end side cap 401, a plurality of
fluid communication ports 401b are formed in a side wall 403, and
one fluid communication port 401a is formed in a bottom wall 404.
Here, no fluid communication port is formed in the trailing end
side cap 402.
Moreover, the temperature sensing element 200 is housed in that cap
400 having the double structure. More specifically, the temperature
sensing element 200 is so housed in the cap 400 that the trailing
end (or trailing end face) 22e of the ceramic substrate 22
constructing the temperature sensing element 200 is positioned on
the more rear side than the trailing end 401c of that of the fluid
communication ports 401b formed in the side wall 403 of the leading
end side cap 401, which is positioned on the most trailing end
side.
For the temperature sensor 300 of Embodiment 2, moreover, in the
cap 400 and between the leading end face of the outer cylinder 3a
of the MI cable 3 and the trailing end face 22e of the ceramic
substrate 22, moreover, there are disposed the vibration-proofing
portion 5 made of insulating cement and the shielding portion 6
made of crystallized glass and positioned on the leading end side
of the vibration-proofing portion 5 and on the more rear side than
the trailing end 401c of that of the fluid communication ports 401b
formed in the side wall 403 of the leading end side cap 401, which
is positioned on the most trailing end side. Moreover, the
vibration-proofing portion 5 stably holds the cores 4 of the MI
cable 3 arranged in the cap 400.
By forming the shielding portion 6 in the cap 400, moreover, the
inside region of the cap 1 is defined across the shielding portion
6 into the front side and the rear side. Even in case the fluid
communication ports 401a and 401b are formed in the cap 400 (i.e.,
the leading end side cap 401), therefore, the exhaust gas
introduced into the cap 1 is blocked by the shielding portion 6
from invading the region on the more rear side than the trailing
end 22e of the ceramic substrate 22. As a result, a foreign
substance such as a moisture content contained in the exhaust gas
can be effectively prevented from sticking through the fluid
communication ports 401a and 401b to the conductive paths, which
are composed of the cores 4 positioned on the rear side of the
ceramic substrate 22.
In the temperature sensor 300 of Embodiment 2, moreover, the
vibration-proofing portion 5 of cement and the shielding portion 6
of crystallized glass can be formed in the cap 400 in the following
manner. First of all, the electric wires 22b of the temperature
sensing element 200 and the cores 4a of the MI cable 3 are jointed
to each other. These connected portions are coated with a
protective film, and the trailing end side cap 402 is then fixed by
laser welding-all-around it to the outer cylinder 3a of the MI
cable 3. After this, a predetermined amount of unsolidified cement
is poured from the leading end side opening of the trailing end
side cap 402, and is dried and solidified to form the
vibration-proofing portion 5. Subsequently, a predetermined amount
of glass powder is poured from the same leading end side opening
and is subjected to a heat treatment to form the shielding portion
6. The leading end side cap 401 having the fluid communication
ports 401a and 401b formed in advance is so fixed on the trailing
end side cap 402 by the laser welding-all-around method as to cover
the temperature sensing element 200.
This temperature sensor 300 can also achieve actions and effects
similar to those of Embodiment 1. By the temperature sensor 300 of
Embodiment 2, too, the axial length (or the leg length) L2 of that
portion of the temperature sensor 300, which is to be exposed to
the inside of the fluid pipe (or the exhaust pipe), can be easily
changed by adjusting the axial length of the MI cable 3, so that
the manufacture cost can be lowered. Moreover, this temperature
sensor 300 is designed to need no change in the axial length of the
ceramic substrate 22 for changing the leg length L2, so that the
vibration-proofing properties of the ceramic substrate 22 can be
retained.
The invention has been described hereinbefore in connection with
Embodiments 1 and 2. However, the invention should not be limited
to those embodiments but could naturally be suitably modified
without departing from the gist thereof. For example, the
vibration-proofing portion 5 should not be limited to one made of
cement but can be made of ceramic fibers (e.g., fibers composed
mainly of alumina and SiO.sub.2).
In Embodiments 1 and 2, moreover, the vibration-proofing portion 5
may be omitted, and the shielding portion 6 may also be formed in
such a mode that it fills up the whole region on the rear side of
the trailing ends 2e and 22e of the ceramic substrates 2 and 22. On
the other hand, the temperature sensors 100 and 300 of Embodiments
1 and 2 may be applied not only to the exhaust temperature sensor
but also to temperature sensors for measuring the intake
temperature of the engine and the temperatures of the air inside
and outside of a room.
This application is based on Japanese Patent application JP
2003-127448, filed May 2, 2003, the entire contents of which are
hereby incorporated by reference, the same as if set forth at
length.
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